Kacper Michajlow: > On Thu, 6 Mar 2025 at 14:31, Andreas Rheinhardt > <andreas.rheinha...@outlook.com> wrote: >> >> Andreas Rheinhardt: >>> Ramiro Polla: >>>> On Tue, Mar 4, 2025 at 6:05 PM Andreas Rheinhardt >>>> <andreas.rheinha...@outlook.com> wrote: >>>>> Ramiro Polla: >>>>>> >>>>>> On 3/4/25 14:42, Andreas Rheinhardt wrote: >>>>>>> (Mostly trivial) patches attached. A branch is at >>>>>>> https://github.com/mkver/FFmpeg/tree/mpegvideo_misc >>>>>> >>>>>> >>>>>> [PATCH 10/40] avcodec/mpegvideo_enc: Move default_mv_penalty to h261enc.c >>>>>> >>>>>>> diff --git a/libavcodec/h261enc.c b/libavcodec/h261enc.c >>>>>>> index dabab9d80a..e33bf35a8a 100644 >>>>>>> --- a/libavcodec/h261enc.c >>>>>>> +++ b/libavcodec/h261enc.c >>>>>>> @@ -46,6 +46,7 @@ static struct VLCLUT { >>>>>>> uint16_t code; >>>>>>> } vlc_lut[H261_MAX_RUN + 1][32 /* 0..2 * H261_MAX_LEN are used */]; >>>>>>> >>>>>>> +static uint8_t mv_penalty[MAX_FCODE + 1][MAX_DMV * 2 + 1]; >>>>>>> static uint8_t uni_h261_rl_len [64 * 128]; >>>>>>> static uint8_t uni_h261_rl_len_last[64 * 128]; >>>>>>> static uint8_t h261_mv_codes[64][2]; >>>>>>> @@ -370,6 +371,8 @@ av_cold int ff_h261_encode_init(MpegEncContext *s) >>>>>>> s->max_qcoeff = 127; >>>>>>> s->ac_esc_length = H261_ESC_LEN; >>>>>>> >>>>>>> + s->me.mv_penalty = mv_penalty; >>>>>>> + >>>>>>> s->intra_ac_vlc_length = s->inter_ac_vlc_length = >>>>>>> uni_h261_rl_len; >>>>>>> s->intra_ac_vlc_last_length = s->inter_ac_vlc_last_length = >>>>>>> uni_h261_rl_len_last; >>>>>>> ff_thread_once(&init_static_once, h261_encode_init_static); >>>>>> >>>>>> This global mv_penalty doesn't seem to be ever initialized; it could be >>>>>> declared const. >>>>> >>>>> But then it would no longer be placed in .bss, but instead in .rodata >>>>> and increase binary size. >>>> >>>> Wow, that's a huge array. >>>> >>>>>> But it also makes me think that whatever code is using this mv_penalty, >>>>>> which is always set to zero, might be calculating things wrong. >>>>>> >>>>> >>>>> It is obviously done to avoid branches for the codecs that matter. H.261 >>>>> does not matter much. Apart from that, it is a very cheap workaround >>>>> given that this table is .bss. >>>> >>>> Could you add some comments (either next to the declaration or the >>>> commit message) to reflect this? (save space from .rodata, and this >>>> being a noop for h.261, which doesn't matter that much) >>>> >>>>>> [PATCH 15/40] avcodec/ituh263enc: Make SVQ1+Snowenc stop calling >>>>>> ff_h263_encode_init() >>>>>> >>>>>>> diff --git a/libavcodec/ituh263enc.c b/libavcodec/ituh263enc.c >>>>>>> index 02da090ba4..8313b2c2c1 100644 >>>>>>> --- a/libavcodec/ituh263enc.c >>>>>>> +++ b/libavcodec/ituh263enc.c >>>>>>> @@ -65,6 +65,127 @@ static uint8_t uni_h263_inter_rl_len [64*64*2*2]; >>>>>> [...] >>>>>>> +static av_cold void h263_encode_init_static(void) >>>>>>> +{ >>>>>>> + static uint8_t rl_intra_table[2][2 * MAX_RUN + MAX_LEVEL + 3]; >>>>>>> + >>>>>>> + ff_rl_init(&ff_rl_intra_aic, rl_intra_table); >>>>>>> + ff_h263_init_rl_inter(); >>>>>>> + >>>>>>> + init_uni_h263_rl_tab(&ff_rl_intra_aic, uni_h263_intra_aic_rl_len); >>>>>>> + init_uni_h263_rl_tab(&ff_h263_rl_inter, uni_h263_inter_rl_len); >>>>>>> + >>>>>>> + init_mv_penalty_and_fcode(); >>>>>>> +} >>>>>>> + >>>>>>> +av_cold const uint8_t (*ff_h263_get_mv_penalty(void))[MAX_DMV*2+1] >>>>>>> +{ >>>>>>> + static AVOnce init_static_once = AV_ONCE_INIT; >>>>>>> + >>>>>>> + ff_thread_once(&init_static_once, h263_encode_init_static); >>>>>>> + >>>>>>> + return mv_penalty; >>>>>>> +} >>>>>>> + >>>>>> >>>>>> This approach kind of hides the rest of h263_encode_init_static() inside >>>>>> ff_h263_get_mv_penalty(), so the name is a bit misleading. I'd expect >>>>>> h263 to still call some init function and ff_h263_get_mv_penalty(), and >>>>>> SVQ1 and Snow to only call ff_h263_get_mv_penalty(), which would only >>>>>> take care of the mv_penalty table. >>>>>> >>>>> >>>>> This would entail using another AVOnce etc. and this level of >>>>> granularity is just not worth it. >>>> >>>> Ok. >>>> >>>>> The name is chosen for what it does for an outsider (i.e. from the >>>>> perspective of svq1enc or snowenc, not the actual H.263 based encoders). >>>> >>>> I'm still not quite happy with the name and how it's used, but it's >>>> good enough so I won't insist. >>>> >>>>>> [PATCH 20/40] avcodec/mpeg4video: Split ff_mpeg4_pred_dc() >>>>>> >>>>>>> diff --git a/libavcodec/mpeg4videoenc.c b/libavcodec/mpeg4videoenc.c >>>>>>> index 64fb96a0cf..26f9b40ff7 100644 >>>>>>> --- a/libavcodec/mpeg4videoenc.c >>>>>>> +++ b/libavcodec/mpeg4videoenc.c >>>>>>> @@ -806,8 +806,14 @@ void ff_mpeg4_encode_mb(MpegEncContext *s, >>>>>>> int16_t block[6][64], >>>>>>> const uint8_t *scan_table[6]; >>>>>>> int i; >>>>>>> >>>>>>> - for (i = 0; i < 6; i++) >>>>>>> - dc_diff[i] = ff_mpeg4_pred_dc(s, i, block[i][0], &dir[i], >>>>>>> 1); >>>>>>> + for (int i = 0; i < 6; i++) { >>>>>> >>>>>> Redeclaring i inside for. >>>>> >>>>> There are other loops which use this i as loop variable. The shadowing >>>>> is IMO less bad than keeping loops in their current form (with iterators >>>>> that don't have loop-scope). >>>> >>>> Agreed. I also prefer scoped iterators. >>> >>> I added a comment to #10 and modified #18 as described. I also changed >>> #21 to protect the macro in parentheses and simplified the FF_RC_OFFSET >>> macro in #31. Furthermore, there are now five more patches. All >>> attached. https://github.com/mkver/FFmpeg/tree/mpegvideo_misc has been >>> force-pushed. >>> >> Will apply this patchset (with the issues pointed out by Ramiro fixed) >> tomorrow unless there are objections. > > After the "Don't count errors from first thread twice" patch, there > are some new UBSAN warnings. > > libavcodec/mpeg12dec.c:2264:37: runtime error: signed integer > overflow: 2147483647 + 99 cannot be represented in type 'int' >
That actually exposes a bug: If two threads have this INT_MAX set, then a third one could make the overall error count to zero (indicating no error) despite the presence of errors. > If we look around there are places where atomic_store(&s->error_count, > INT_MAX); is done. > > I don't think this change caused the issue, because overflows would > also happen before, but it looks like UBSAN doesn't instrument atomic > variables, so it was hidden. Overflow for atomic variables are not undefined: "For signed integer types, arithmetic is defined to use two’s complement representation with silent wrap-around on overflow; there are no undefined results." > > Would you take a look? > Yes. - Andreas _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
